The natural teeth of an individual may be lost as a result of dental disease or trauma, making it desirable to replace such teeth with one or more prosthetic devices. An example of a prosthetic device is the dental implant which is surgically positioned within the mandibular or maxillary alveolar bone.
One type of dental implant has a first implant member for placement in an osteotomy site in the alveolar bone of a patient. Following healing, a head member, commonly called an abutment, is mounted in or on the first implant member and a tooth simulating prosthesis or crown is then mounted on the abutment. A successful system of this type is disclosed in U.S. Pat. No. 4,738,623. In this patent, a first implant or root member having a first or outer end formed with a female socket circumscribed by a shoulder and having a suitable anchoring means, such as outwardly extending fins, is placed in an osteotomy site or implant receiving cavity formed in the alveolar bone with suitable surgical instruments and techniques. The first implant member is inserted into the cavity with the upper portion of the member a selected distance below the opening of the cavity, that is, below the crest of the bone, e.g., two or three millimeters. A healing plug in inserted into the female socket of the first implant member and particles of a natural and/or synthetic bone growth stimulating grafting material are then packed within the cavity around the shoulder of the implant member and the wound is then closed.
Following healing, the dentist accesses and removes the plug and replaces it with an abutment. The abutment has a male portion received within the female socket and an intermediate, outer generally hemispherical surface portion which may extend through the surface of the gingiva and preferably through the surface of the crest of the bone which may have been previously reamed to form a complimentary configuration when forming the cavity. A prosthetic device can then be attached to the abutment forming a smooth continuous surface with the hemispherical surface portion of the abutment with the interface between the prosthetic device and the abutment being supragingival or, for best aesthetics, subgingival, that is, being covered by the gingival tissue. Fabrication of the prosthetic device typically involves making an impression, generally a full arch impression, and pouring a model forming, inter alia, a positive replica, or die, of the abutment head. A laboratory technician then burnishes platinum foil over the die which serves as a core on which a prosthesis is built. Upon completion and firing of the prosthesis, the platinum is scratched away. Although this procedure has been acceptable, the efficacy of the result is dependent upon the skill of the technician and is highly labor intensive and time consuming. Alternatively, the technician could fabricate the prosthesis by a lost wax technique utilizing a central core of metal, usually a gold palladium alloy, onto which porcelain powders are added and fused in a firing oven.
In coassigned U.S. Pat. No. 6,290,500, an abutment is described and claimed in which laboratory procedures, concomitant expenses and time delays are substantially reduced. In that patent, the subject matter of which is incorporated herein by this reference, a dental implant abutment is disclosed having a central portion between a post portion and a head portion in which a circumferentially extending shelf is formed between the base of the head portion and the central portion which forms an angle with a plane perpendicular to the longitudinal axis of the head portion within a range of approximately 0–30 degrees. A prosthesis which may or may not include a sleeve core is closely fitted to the head portion and is provided with an end face at the entrance to a head receiving cavity matching the shoulder of the abutment.
In one embodiment, an integrated abutment crown is formed by providing a sleeve having an internal configuration with a negative image closely matching the outer surface of the head portion of an abutment so that the sleeve can be fitted precisely onto the head portion. The sleeve is placed on the head portion of a temporary or removable abutment having the same head portion configuration and having a post removably inserted in the bore of an implant positioned in an osteotomy site. An impression of moldable material is taken of the removable abutment and the area adjacent to the osteotomy site. The impression is removed from the patient's mouth with the sleeve remaining in the impression. A transfer abutment having a head portion with the same configuration is placed within the sleeve and the transfer abutment is inserted in an implant analog. Molding material is then poured into the impression to form a model or replica of the area adjacent to the osteotomy site with the implant analog locked in the model. The model is removed from the impression and the sleeve is removed and positioned on the transfer abutment in the model. A prosthesis is then built on a sleeve by adding suitable material and the material is shaped to fit within the available space between teeth or prosthesis contiguous to and opposing the osteotomy site. The prosthesis is then attached to a permanent abutment having a head portion with the same configuration, as by cementing or bonding, to form an integrated abutment crown. The integrated abutment crown can then be polished extraorally to remove extraneous cement when cement is used as the means of attachment and then the finished abutment can be inserted into the bore of an implant. When the post of the abutment and the bore of the implant have matching self-holding tapers, the angular position of the integrated abutment crown can be adjusted to any desired orientation and then locked in place by tapping the integrated abutment crown with a selected force. As noted in the U.S. Pat. No. 6,290,500 patent, cylindrical posts having no taper can also be used and adjusted angularly and then cemented or glued into the implant.
A special jig is provided in the patent for use with the self-holding abutment attaching system for ensuring that the locking force is imparted to the integrated abutment crown by a force which is essentially collinear with the longitudinal axis of the post portion and implant bore in a way that does not mar the surface of the crowned portion.
In a modified embodiment, a prefabricated crown element is selected for placement on the head of the removable attachment, either with or without the use of a sleeve core. A cavity is provided, or is formed, in the prefabricated crown element and adapted to receive the head portion of an abutment, or the sleeve, as described above, and the outer configuration is adapted to fit between contiguous and opposing teeth or prosthesis relative to the osteotomy site to form a finished crown. The finished crown is then attached to an abutment having a self-holding tapered post extraorally to form an integrated abutment crown for subsequent insertion into an implant having a matching self-holding tapered bore positioned within the osteotomy site. The integrated abutment crown is polished extraorally and inserted into the implant and its angular position adjusted and fixedly locked in place.